1. Field of the Invention
The present invention relates generally to portable flashlights and, more specifically, to an improved twist switch for establishing electrical contact between the flashlight bulb and a dry cell battery contained within the flashlight body.
2. Description of the Prior Art
Flashlights of varying sizes and shapes are well known in the art. A number of such designs are known which utilize two or more dry cell batteries, carried in series in a tubular body which serves as a handle for the flashlight, and as their source of electrical energy. Typically, an electrical circuit is established from one terminal of the battery through a conductor to an external switch and then through a conductor to one contact of a bulb. After passing through the filament of the lamp bulb, the electrical circuit emerges through a second contact of the lamp bulb in electrical contact with a conductor, which in turn is in electrical contact with the flashlight housing. The flashlight housing provides an electrical conduction path to an electrical conductor, generally a spring element, in contact with the other terminal of the battery. Actuation of the external switch to complete the electrical circuit enables electrical current to pass through the filament of the lamp bulb, thereby generating light which is typically focused by a reflector to form a beam of light.
A number of disadvantages result from the use of a switch mounted on the side of the tubular body of the flashlight. Such switches are easily damaged when subjected to severe environments. Switches of this type can also be turned on by accident, such as where vibration causes electrical contact. Because of the arrangement of internal components, the overall length of the flashlight is increased
In order to overcome these shortcomings, a number of prior art designs are known in which an end cap is rotatably secured to the flashlight body, the end cap being rotated to establish the required electrical contact to illuminate the lamp bulb. A number of such prior art designs feature rotatable end caps which are rotated to cause longitudinal movement of the dry cell batteries within the flashlight body in the direction of the lamp bulb, thereby causing contact between the battery center terminal and the base contact of the lamp bulb. In the open position, the dry cell battery is typically spring biased away from the base contact of the bulb. Examples of such designs are shown, for instance, in U.S. Pat. Nos. 2,258,074; 2,435,689; 2,249,689; and 1,595,146.
In more recent improvements, miniature flashlights have been designed which feature a rotatable switch located in the reflector end of the flashlight body. The lamp bulb is located within an insulated receptacle at the reflector end of the flashlight with one or more conductive pins being rotatably aligned by movement of the switch portion of the device to establish electrical contact While the switch mechanisms are internal to the device and are thus less subject to damage, they are overly complicated in design and more costly to manufacture. Such designs are shown, for instance, in U.S. Pat. Nos 4,899,265; 4,916,588; 4,907,141; 4,864,474; and 4,658,336.
The present invention has as its object to provide an improved twist switch for a portable flashlight which is simple in design and economical to manufacture.
Another object of the invention is to provide such a switch which is not subject to accidental actuation due to vibration, or the like.
Another object of the invention is to provide an improved flashlight design which is shorter in overall length through the elimination of an external switch mounted on the side of the tubular body of the flashlight.
Another object of the invention is to provide a twist switch for a flashlight which is self-cleaning in operation.